Biodegradable cross-linked alkyl polysaccharide dispersion material coated on lignocellulose sheets

Abstract

The present invention relates to biodegradable cross-linked alkyl polysaccharide dispersion materials for coating on lignocellulose sheets as a promising alternative to traditional plastic mulch in sustainable agricultural practices and process for preparation thereof. More particularly, the present invention relates to biodegradable cross-linked alkyl polysaccharide dispersion coating material coated on lignocellulose sheets having tensile strength 15‒20 MPa, tensile index of 25‒30 N.m / g wherein the coating dispersion material is obtained from the Michael addition reaction of polysaccharide (chitosan), acrylic crosslinker and further alkylation in presence of alkylamine in 93%‒95%yield. The aim of the invention is to mitigate environmental pollution and reduce dependence on non-renewable resources. The present invention provides a method of coating to prepare water repellent lignocellulose sheet / paper with a stability of 50‒70 days in outdoor environmental conditions and biodegradation in soil within 30‒45 days.

Description

[0001] BIODEGRADABLE CROSS-LINKED ALKYL POLYSACCHARIDE DISPERSION MATERIAL COATED ON LIGNOCELLULOSE SHEETS

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to biodegradable cross-linked alkyl polysaccharide coating dispersion material for lignocellulose sheets and papers as alternative to non-degradable plastic mulches and process for preparation thereof. More particularly, the present invention relates to biodegradable cross-linked alkyl polysaccharide dispersion coating material coated on lignocellulose sheets resulting in tensile strength of 15-20 MPa, tensile index of 25-30 N.m / g wherein the coating dispersion material is obtained from the Michael addition reaction of polysaccharide (chitosan), acrylic crosslinker and further alkylation in presence of alkylamine in 93%-95% yield. Additionally, as prepared biodegradable cross-linked alkyl polysaccharide coating dispersion material is applied on lignocellulose sheets which are applicable as mulch in farming to enhance the soil health by conserving the moisture, reducing soil erosion, suppressing weeds and an alternative to conventional plastic mulches. The present invention provides a coating process and biodegradable cross-linked alkyl polysaccharide dispersion material to prepare water repellent lignocellulose sheet / paper with a stability of 50-70 days in outdoor environmental conditions and biodegradation in soil within 30-45 days.

[0004] BACKGROUND OF THE INVENTION

[0005] In modern farming practices to provide various benefits to soil health, plant growth, and overall crop production mulches play a crucial role. The mulches are materials applied to the soil surface around plants to modify their immediate environment. They can be categorized into organic such as cellulose sheets, wood chips, and synthetic like plastic films. The organic mulches suppress weed growth by blocking light to the soil surface, thus inhibiting weed seed germination and growth. Also act as insulators, moderating soil temperature fluctuations which are beneficial for maintaining optimal root growth conditions and protecting plants from temperature extremes. The mulches also help to prevent soil erosion or the loss of fertile topsoil. While they offer numerous benefits, their effectiveness depends on factors such as mulch type, application method, local climate, and specific crop requirements. The type of mulches requires careful consideration to optimize their benefits without unintended negative consequences. Their application requires understanding of local conditions and careful management to maximize their positive effects on soil health and crop performance. The conventional mulches such as plastic mulches help to control certain environment factors such as weeds, moisture content and also preserve the soil temperature, decrease the use of herbicides and improve the quantity and quality of the crop, fruits and vegetables. These are often made from non-biodegradable materials, which contribute to environment pollution. These mulches can pertain in the soil for years after use, which affect the soil health and wildlife. These also raise soil temperatures significantly therefore, are not suitable for hot climates or during summer season.

[0006] Further, the plastic mulches conserve soil moisture by reduction in evaporation and prevent water infiltration into the soil which leads to potential waterlogging, also alter natural soil processes such as aeration and microbial activity, restrict the decomposition of organic matter, affecting nutrient cycling and soil structure over time. In addition to increasing labor and waste management expenses, plastic mulches must be removed and disposed of correctly after usage in order to prevent problems like tearing, flying away in the wind. Furthermore, the restricted disposal of polyethylene mulches needs the use of landfills which is expensive and also responsible for releasing plastic materials into the atmosphere. Therefore, more effective selfdecomposing organic mulches should be used in favor of polyethylene-based mulches, which pollute the soil.

[0007] Therefore, lots of efforts and research has been dedicated for the preparation of hydrophobic paper mulches by using the laminate of low-density polyethylene (LDPE) which is a synthetic non-degradable polymer. In recent years, the LDPE coated paper mulches became popular which are able to improve all the required properties of synthetic mulches. However, the main drawback is separating the coated polymer layer from the paper which is quite difficult. Therefore, the decomposition or recyclization of these LDPE coated paper mulches present great challenge. In order to avoid the use of such synthetic non-biodegradable polymer, the surface modification of papers was done by silanization using low molecular weight alkyl and fluoroalkyl silanes, silane-modified epoxidized downstream corn oil. The surface modification by alkyl silanes could only improve the water resistance of papers, whereas the same with fluoroalkyl silanes showed both the water and oil resistance. Since, fluoroalkyls were getting banned because they are toxic and persistent in nature, there was an opportunity to replace them by finding some greener alternatives.

[0008] Hence, the biopolymers like polysaccharides, proteins, lipids or waxes were chosen and employed as paper coating because of their renewability, biocompatibility, biodegradability and low cost. However, the limitation with these biopolymers is their hydrophilic property. In order to achieve the water repelling properties, there was an immense need to develop a coating of synthetic biodegradable polymers like poly-3-hydroxybutyrate (PHB) and polylactic acid (PLA) that were capable to improve the water resistance of papers. However, they were not suitable for commercial application because of brittleness and high cost associated to manufacturing.

[0009] The biodegradable coated lignocellulose sheets have several environmental benefits and practical advantages in agriculture as compared to conventional plastic mulches. These mulches are coated with organic (cross-linked polysaccharides) dispersion material that can be made from renewable resources, these lignocellulose sheets also decompose naturally in soil over time, reducing environmental pollution in comparison to persistent plastic residues. The key benefits of these organic mulches include improved soil health and fertility also promote microbial activity and contribute organic matter to the soil as they decompose, enhancing overall soil structure and nutrient availability for plants. The coated lignocellulose mulches are lightweight, easy to install, and can be customized to fit around plants or cover large areas efficiently.

[0010] The lignocellulosic materials are cost effective, non-toxic and biodegradable, making them an attractive option to replace polyethylene -based mulches. However, the lignocellulose sheets directly are not applicable for mulching due to their poor mechanical and water resistance properties. Herein, in present invention we have developed a coating dispersion material, suitable for lignocellulose sheets / papers to improve their mechanical durability and water resistance required for mulching. More particularly the present invention concerns a biodegradable cross-linked alkyl polysaccharide coating dispersion material for lignocellulose sheets which is obtain from further alkylation by Michael addition reaction between polysaccharide (chitosan), acrylic crosslinker and alkylamine. The invention surprisingly has very good mechanical strength compared to other available organic mulches and may be suitable for mulch in agriculture to improve the health of the soil.

[0011] Reference may be made to the Japanese patent JP2640308B2 discloses a sheet to be used for the growth promotion of agricultural crops, easy to bum after use, and readily decomposable even if mixed with soil, by providing a substrate made of paper with a light- shielding layer. In this invention along with biodegradable material such as starch, polyvinyl alcohol, acrylic emulsion was used which increased the cost of the mulch and incorporated nonbiodegradability to the mulch. Hydrophobicity and mechanical properties of the mulch were not discussed which introduce drawback for mulching application in different environment conditions.

[0012] Reference may be made to Chinese Patent application CN 103183840A discloses water resistance and excellent mechanical property of crosslinked composite membrane of biodegradable chitosan which is chemically bonded by polyoxyethylene glycol as the linking agent. For making such type of crosslinked system high temperature (110 °C) required which is not suitable for commercial application as it consume more power. Moreover, the mulching application was not examined.

[0013] Reference may be made to Patent Application WOS000299378307171 wherein, the synthesis and characterization of amphoteric and amphiphilic chitosan derivatives is disclosed with their use for multi-functional papermaking wet-end additive to produce reduced thermal stability and degree of crystallisation. In this invention, amphoteric and amphiphilic chitosan was used only to improve the paper making process. However, mulching application was not explored.

[0014] Reference may be made to the European patent EP0323732 discloses the dry and wet strength of composite sheet. In this invention relates to formation of composite sheet having bio-based materials such as cellulose and chitosan which make this sheet biodegradable in soil. However, hydrophobicity of the composite sheet and mulching application were not explored.

[0015] Reference may be made to the Japanese patent JP02002303A wherein, the formation of biodegradable sheet substrate by using 1-10% (pulp basis) chitosan with permeability of gas and moisture is disclosed. These sheets have good wet strength which makes this sheet useful for nursery seedling covers. However, the said invention involves conventional paper making approach with less hydrophobicity.

[0016] Reference may be made to the research article published in Cellul. Chem. Technol, 47(7-8), 623-630 by Nicu et al., which discloses synthesis of alkyl-chitosan as paper coating material to improve water barrier properties using different alkyl chain lengths (octyl-ACh8, decylAChlO and dodecyl-AChl2) for water barrier properties. The water barrier properties of paper were evaluated by contact angle (CA), water absorption capacity (Cobb60 index) and water vapour transmission rate (WVTR). The mechanical properties of coated paper were not mentioned, which is very important for mulching application. The reaction time was also more and coating process was very complex. Reference may be made to the article published in Polymer International, 60(6), 963-969.” published by A.B. Reis et al., which discloses environment-friendly coating of kraft paper by an emulsion which contains chitosan and lipid (like palmitic acid and stearic acid). The coated kraft paper showed significantly lower water vapor permeability rate (WVPR) (by 51%) and water absorption capacity (by 41%) as compared to uncoated kraft paper. However, the biodegradability and water contact angle were not mentioned here. Also, the mulching application was not explored.

[0017] Reference may be made to the article published in ACS Sustainable Chemistry & Engineering, 10(14), 4694-4704 wherein the preparation of chitosan grafted with long alkyl chains the coating material for cotton fabric is disclosed. The coated cotton showed superhydrophobicity with WCA of 161.4°±3. However, the paper coating and mulching applications were not explored in this article.

[0018] Reference may be made to the article published in ACS Sustainable Chemistry & Engineering, 8(13), 5147-5155 which discloses the chemical modification of chitosan by grafting polydimethylsiloxane (PDMS), zein particles etc. to achieve the water and oil-resistant property in coated kraft papers. Such chemical modifications were able to improve the water resistance and barrier properties of the paper. However, PDMS is non-degradable polymer and as long as coatings use non-biodegradable polymers, plastic pollution will exist. In addition, the biodegradability and mulching application of the coated kraft papers were not explored.

[0019] Reference may be made to the article published in ACS Appl. Polym. Mater. 2024, 6, 6, 3263- 3272 which discloses the synthesis of polymeric waxes for kraft paper coating. The coated paper showed good oil and water repelling properties, moisture barrier, biodegradability and recyclability. These properties make the coated paper ideal for packaging application. However, mulching application was not explored here.

[0020] The research article published in ACS Sustainable Resour. Manage. 2024, 1, 5, 879-889 by Rabnawaz et al. wherein; the coating of the kraft paper by putting waterborne acrylated epoxidized soybean oil followed by photo curing is disclosed. The coated paper showed good oil and water repelling properties, high mechanical strength and biodegradability. However, mulching application was not explored here.

[0021] From a review of the literature, it may be postulated that none of the prior arts discloses biodegradable cross-linked alkyl polysaccharide coating dispersion material with high tensile strength for lignocellulose sheets for practical farming needs such as mulching. In recent years, the sheet or paper coating research is directed towards using fluorine-free materials and more use of bio-based materials in the coating composition. The bio-based materials for coating offer environment friendly alternatives to traditional petroleum-based coatings. In this regard, Chitosan was found to be quite promising because of their biocompatibility and biodegradability.

[0022] To the best of our knowledge, there is no report till date on developing a biodegradable crosslinked alkyl polysaccharide coating dispersion material for lignocellulose sheets / paper with high tensile strength, obtain by Michael addition of polysaccharides, acrylate crosslinker and alkyl amine from bio-sourced raw materials focusing on the application in mulching.

[0023] The following discussion presents a review of the existing literature pertaining to the biodegradable polysaccharide coating dispersion material, rendering an overview of the prior art references in this field. These references serve as a testament to the extensive research conducted in this area and provide valuable insights into the techniques and methodologies employed in the production process. The above information disclosed is only for the enhancement of understanding of the background of the invention.

[0024] Accordingly, keeping in view the drawbacks of the hitherto reported prior arts, the present invention realized that there is an immense need to develop a biodegradable coated dispersion material for the lignocellulose sheets for mulching of crops. More specifically a cross-linked alkyl polysaccharide coating dispersion material for lignocellulose-based sheets or papers which are, water resistant, stable in outdoor environmental conditions at least for single crop season; also that self decomposes in the soil without leaving any harmful residues as compare to conventional plastic mulches.

[0025] OBJECTIVE OF THE INVENTION

[0026] The main objective of the present invention is to provide a biodegradable cross-linked alkyl polysaccharide coating dispersion material for lignocellulose-based sheets or papers having high tensile strength, tensile index for viable, sustainable solution for modem agriculture and horticulture, addressing both environmental concerns and practical farming needs by applying eco-friendly alternative to existing plastic mulches.

[0027] Another objective of the present invention is to provide a biodegradable crosslinked alkyl polysaccharide dispersion coating material wherein the coating dispersion material is obtained from the Michael addition reaction of polysaccharide (chitosan), acrylic crosslinker and further alkylation in presence of alkylamine resulting biodegradable cross-linked alkyl polysaccharide dispersion coating materials in 93%-95% yield.

[0028] Another objective of the present invention is to provide a process for the preparation of biodegradable crosslinked alkyl polysaccharide dispersion coating material.

[0029] Another objective of the present invention is to provide a biodegradable crosslinked alkyl polysaccharide dispersion coating material having minimal water absorption property as compare to uncoated sheets, with enhanced water repelling property for in outdoor environment and decompose naturally in the soil.

[0030] Yet another objective of the present invention is to provide a method for coating of biodegradable crosslinked alkyl polysaccharide dispersion material on lignocellulose sheets via dip coating method.

[0031] These objectives of the present invention, as well as other objectives related thereto, will be readily apparent post consideration of the description of the invention, together with reference to the contents of the FIG.s of the drawings. Additional objects, advantages and other novel features of the invention will appear as the description proceeds and in part will become apparent to those skilled in the art upon examination of the following.

[0032] The disclosure highlights the objectives of the invention, its distinctive features, and various innovations. To gain a better grasp of the invention, its operational benefits, and the specific goals it achieves, referring to the accompanying drawings and descriptive content, which showcase preferred embodiments of the invention, would be beneficial.

[0033] SUMMARY OF THE INVENTION

[0034] Additional features and embodiments of the present disclosure will be better understood through the techniques and other aspects of the disclosure. Other embodiments of the invention are described in detail herein and are considered a part of the claimed disclosure.

[0035] The following is a condensed description of the disclosure to give the reader with a basic understanding. Its main goal is to present some of the principles described in this document in a simpler version as a prologue to the more extensive exposition that follows.

[0036] In accordance with the main aspect the present invention provides a biodegradable cross-linked alkyl polysaccharide dispersion coating material for lignocellulose sheets, comprises;

[0037] (a) a polysaccharide; (b) an acrylic crosslinker;

[0038] (c) an alkyl amine R(CH2)nNH2.

[0039] In another aspect, the molar ratio of the acrylate cross-linker and the alkyl amine is 1:3.

[0040] In another aspect, the biodegradable cross-linked alkyl polysaccharide dispersion material is prepared by the Michael addition reaction of the polysaccharide, and the acrylic cross-linker followed by alkylation with the alkylamine.

[0041] In another aspect, the biodegradable cross-linked alkyl polysaccharide dispersion coating material is obtained in 93%-95% yield.

[0042] In another aspect, the biodegradable crosslinked alkyl polysaccharide dispersion coating material in the present invention, wherein a linear polysaccharide selected from chitosan and the acrylate crosslinker is selected from trimethylolpropane triacrylate, pentaerythritol triacrylate (PET) and a mixture thereof.

[0043] In another aspect, the weight ratio of polysaccharide and acrylate cross-linker is 1:3 to 1:5.

[0044] In another aspect, the biodegradable crosslinked alkyl polysaccharide dispersion material in the present invention, wherein the alkyl amine selected from methyl amine, ethyl amine, 1- propyl amine (n-propyl amine), 2-propyl amine, ethyl -propyl amine, methyl-hexyl amine, ethyl-methyl amine, cycloalkyl amine, octadecyl amine, alkenyl amine, alkynyl amine, aryl amine, arylalkyl amine, alkylaryl amine and a mixture thereof; and n in R(CH2)nNH2 comprises alkyl chain of 2-18 carbon atoms.

[0045] In another aspect, the biodegradable crosslinked alkyl polysaccharide dispersion material in the present invention, wherein lignocellulose sheet / paper is selected from kraft paper, copy paper, card stock, news print, watercolour paper, Vellum, tracing paper, parchment paper and construction paper.

[0046] In another aspect, the present invention provides a process for preparation of biodegradable crosslinked alkyl polysaccharide dispersion coating material coated lignocellulose sheets, comprises the steps of;

[0047] (a) preparing aqueous solution of chitosan in acetic acid, and adding an acrylate crosslinker, the said solution was heated in water bath at temperature in the range of 50°C-70 °C and stirred at 200-300 rpm for period in range of 1-3 hours; (b) adding ethanolic solution of alkyl amine drop-wise to the reaction mixture as prepared in step a) and keeping the reaction conditions constant for period in range of 1-3 hours gives a hazy dispersion;

[0048] (c) cooling down the hazy dispersion aa obtained in step b) to room temperature the range of 20°C-30 °C and store in air tight container;

[0049] (d) diluting the dispersion material as obtained in step c) with deionized water to the five times and apply it for dip coating dispersion on lignocellulose sheets;

[0050] (e) air-drying lignocellulose sheets obtained from step d at room temperature in range of 20- 30°C for the period in range of 24-48 h.

[0051] In another aspect, the present process for preparation of biodegradable crosslinked alkyl polysaccharide dispersion material coated o lignocellulose sheets contains the acrylate cross linker and alkyl amine in the molar ratio 1:3.

[0052] In another aspect, the present process for preparation of biodegradable crosslinked alkyl polysaccharide dispersion material coated on lignocellulose sheets comprises dispersion solution with solid content at 1.6-2.6 wt% and the dimension of lignocellulose sheets are 36 x 48 inches for mulching of plants with crop duration of more than 50-70days.

[0053] In another aspect, the present invention provides a biodegradable crosslinked alkyl polysaccharide coated lignocellulose sheets having water absorption of 42.8 % compare to uncoated sheets 127.3% in 4 h, with enhanced water repelling property for 2-3 months in outdoor environment and decompose naturally in the soil within 30-45 days.

[0054] In another aspect, the present invention provides biodegradable crosslinked alkyl polysaccharide coated lignocellulose sheets in having different molar concentration (17-26 mmol) of alkyl chain have higher tensile strength 15-20 MPa with a tensile index of 25-30 N.m / g and tensile strength of 2450-2650 N / m.

[0055] Yet another aspect, the present invention provides a method for coating of biodegradable crosslinked alkyl polysaccharide dispersion material on cellulose sheets comprises the steps of; (a) preparing crosslinked alkyl polysaccharide coating dispersion impregnated with chitosan;(b) coating of dispersion solution obtained in step a) on the lignocellulose sheets;(c) air-drying lignocellulose sheets from step b) at room temperature for 24-48 h. In summary the present invention involves process for preparation of biodegradable dispersion coating materials of cross-linked alkyl chitosan using acrylate cross-linker, alkyl amine via Michael addition method followed alkylation and the biodegradable dispersion materials is coated over ordinary lignocellulose sheets or paper by dip-coating method. The coated sheets have significant improvement in hydrophobic properties and mechanical strength. The coated sheets also retained physical and mechanical properties in outdoor exposure for more than two months which confirm the robustness of the coating. The coated paper is bio-compostable and has the potential to be applied for mulching application in agriculture field.

[0056] Further aspects of the technology described herein will be brought out in the following portions of the specification, wherein the detailed description is for the purpose of fully disclosing preferred embodiments of the technology without placing limitations thereon.

[0057] Brief Description of the Drawings

[0058] To complete the description and in order to provide for a better understanding of the present invention, a set of drawings is provided. The drawings form an integral part of the description and illustrate an embodiment of the present invention, which should not be interpreted as restricting the scope of the invention, but just as an example of how the invention can be carried out. The drawings comprise the following FIG.s:

[0059] FIG. 1. Depicts the structural framework and Complete reaction pathway to prepare crosslinked alkyl chitosan.

[0060] FIG. 2. Illustrates the coating process to develop biodegradable coated paper resulting significant water repelling property required for mulching application.

[0061] FIG. 3. Shows a) Aqueous dispersion of crosslinked alkyl chitosan, b) Dip-coated lignocellulose sheets / papers, c), d) and e) Coated lignocellulose sheets / papers prevented the wetting of the coated interface by juice, milk and water, f) & g) Illustrating the repelling property by milk, juice and water on the coated part, h) Coated lignocellulose sheets / papers kept outdoor for the testing of weather ability and durability, i) The non- wettability performance of coated lignocellulose sheets / papers with high flow of water after 60 days of outdoor aging.

[0062] FIG. 4. Depicts the water uptake profiles of coated and uncoated lignocellulose sheets / papers at different time interval. FIG. 5. Shows the decomposition of coated lignocellulose sheets / papers in compost in every 15 days with FE-SEM images at before and after 30 days.

[0063] FIG. 6. Depicts the Images of the coated lignocellulose sheets / papers used as mulch for the productive melon cultivation at the outskirts of Hyderabad.

[0064] DETAIL DESCRIPTION OF THE INVENTION

[0065] The following description is not to be taken in a limiting sense but is given solely for the purpose of describing the broad principles of the invention. Embodiments of the invention will be described by way of example, with reference to the above-mentioned drawings showing elements and results according to the present invention.

[0066] The foregoing detailed description of the disclosure is elaborated to provide a clear understanding to the person who is skilled in the art. Additional features, embodiments and advantages of the invention will be described hereinafter which form the subject of the claims of the disclosure, However, the set forth disclosure provide in the specification will best be understood in conjunction with the appended claims and FIG.s as provide heretofore. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present disclosure. It should also be realized by those skilled in the art that such equivalent processes do not depart from the spirit and scope of the disclosure as set forth in the appended claims. It will be readily understood that the aspects of the present disclosure, as generally described herein, and illustrated in the FIG.s, can be arranged, substituted, combined, and designed in various configurations, all of which are explicitly contemplated and make part of this disclosure.

[0067] While the invention has been disclosed with reference to certain embodiments, it will be understood by those skilled in the art that various changes may be made, and equivalents may be substituted without departing from the scope of the invention. In addition, many modifications may be made to adapt to a particular situation or material to the teachings of the invention without departing from its scope.

[0068] Throughout the specification and claims, the following terms take the meanings explicitly associated herein unless the context clearly dictates otherwise. The meaning of "a", "an", and "the" include plural references. The meaning of "in" includes "in" and "on." Referring to the FIG.s, like numbers indicate like parts throughout the views. Additionally, a reference to the singular includes a reference to the plural unless otherwise stated or inconsistent with the disclosure herein.

[0069] The present invention provides a biodegradable cross-linked alkyl polysaccharide dispersion coating material coated over lignocellulose sheets having tensile strength 15-20 MPa, tensile index of 25-30 N.m / g wherein the coating dispersion material is obtained from polysaccharide (chitosan), acrylic crosslinker and alkylamine by Michael addition reaction followed by alkylation resulting a 93%-97% yield, comprises;

[0070] (a) a polysaccharide;

[0071] (b) an acrylic crosslinker;

[0072] (c) an alkyl amine R(CH2)nNH2; and

[0073] (d) a lignocellulose sheet / paper.

[0074] The polysaccharide in the present invention involves Chitosan, which is a well-known biosourced polysaccharide. The chitosan has a linear structural framework, to develop a biodegradable crosslinked polysaccharide structure it is functionalized with further alkylation as present in (FIG. 1) wherein the alkyl groups present have C15-C18 carbon atoms and the acrylic crosslinker is selected from trimethylolpropane triacrylate, pentaerythritol triacrylate (PET) and a mixture thereof.

[0075] The alkyl amine used in the present invention is selected from methyl amine, ethyl amine, 1- propyl amine (n-propyl amine), 2-propyl amine, ethyl -propyl amine, methyl-hexyl amine, ethyl-methyl amine, cycloalkyl amine, octadecyl amine, alkenyl amine, alkynyl amine, aryl amine, arylalkyl amine, alkylaryl amine and a mixture thereof; and n in R(CH2)nNH2 comprises alkyl chain of 2-18 carbon atoms.

[0076] In the preferred embodiment, the lignocellulose sheet / paper is selected from kraft paper, copy paper, card stock, news print, watercolour paper, Vellum, tracing paper, parchment paper and construction paper.

[0077] In another embodiment of the present invention provides a biodegradable crosslinked alkyl polysaccharide coated sheet having water absorption of 42.8 % compare to uncoated sheets 127.3% in 4 h, and the water uptake is 14.3% per hour for coated sheets compare to the uncoated sheets (118.2% per hour absorption with enhanced water repelling property for 2-3 months in outdoor environment and decompose naturally in the soil within 30-45 days. In another embodiment of the present invention provides biodegradable crosslinked alkyl polysaccharide coated lignocellulose sheets coated with different molar concentration (17-26 mmol) of alkyl chain have higher tensile strength 15-20 MPa with a tensile index of 25-30 N.m / g and tensile strength of 2450-2650 N / m.

[0078] In another embodiment of the present invention provides a method for coating of biodegradable crosslinked alkyl polysaccharide dispersion material on lignocellulose sheets comprises the steps of;

[0079] (a) preparation of crosslinked alkyl polysaccharide coating dispersion impregnated with chitosan;

[0080] (b) coating of dispersion solution obtained in step a) on the lignocellulose sheets;

[0081] (c) air-drying lignocellulose sheets from step b) at room temperature in range of 20-30 °C for the period in range of 24-48 h. The biodegradable crosslinked Chitosan based coating material in the present invention coated the form of aqueous dispersion on lignocellulose sheets via dip-coating approach as illustrated in present invention FIG. 2.

[0082] In another embodiment of the present invention provides a process for the preparation of biodegradable crosslinked alkyl polysaccharide dispersion materials comprises the steps of;

[0083] (a) preparing aqueous solution of chitosan in acetic acid, and adding pentaerythritol triacrylate (PET), the said solution was heated in water bath at temperature in the range of 50°C-70 °C and stirred at 200-300 rpm for period in range of 1-3 hours;

[0084] (b) adding ethanolic solution of alkyl amine drop-wise to the reaction mixture as prepared in step a) and keeping the reaction conditions constant for period in range of 1-3 hours gives a hazy dispersion;

[0085] (c) cooling down the hazy dispersion aa obtained in step b) to room temperature the range of 20°C-30 °C and store in air tight container;

[0086] (d) diluting the dispersion material as obtained in step c) with deionized water to the five times and apply it for dip coating dispersion on lignocellulose sheets.

[0087] In another embodiment of the present invention provides as synthesized coating material is diluted 4-6 times to prepare a coating solution, the said solution is coated over the lignocellulose sheets or paper via dip coating method and air dried at the room temperature. The coated sheets developed in the present embodiment have resistance toward various kinds of liquid solutions such as milk, juice and water as illustrated in FIG. 3 which are easy to wipe off from the surface of coated sheets. The coated lignocellulose sheets preserve the liquid resistibility after exposure of 50-70 days outdoor environmental conditions and also under heavy flow of water.

[0088] The coated lignocellulose sheets or papers have significant improvement in their water repelling and mechanical properties therefore can work as eco-friendly alternative to the single use plastic mulches. The biodegradable dispersion coating has a promising potential towards reducing plastic waste and facilitating a transition towards more sustainable alternative for single use plastic. These coated sheets have water repelling property as mulching films during the crop season (usually 2-3 months).

[0089] The present invention also provides the water uptake percentage per hour and after four hours for cross-linked Chitosan coated sheets and uncoated sheets in FIG. 4. The uncoated paper showed high water uptake value (118.2%) in 1 hour of dipping whereas the coated paper showed only 14.3% absorption. The maximum water absorption for uncoated paper reached to 127.3% in 4 hours, the same for coated paper was 42.8 %.

[0090] The present invention as illustrated in FIG. 5 shows the FE-SEM images illustrating the dramatic change in lignocellulose fibres morphology of the coated sheets / paper biodegradation in 30 days and the stages of degradation at every 15 days for 45 days observing breakage and fragmentation of the coated lignocellulose sheets.

[0091] The present invention as illustrated in FIG. 6 depicts Images of the coated lignocellulose sheets / papers for mulching in melon crops cultivation at the outskirts of Hyderabad and the as prepared coated lignocellulose mulch is an alternative to traditional plastic-based mulching materials, providing similar benefits while reducing waste and environmental impact.

[0092] Table 1 depicts comparative data of coated sheets with different molar concentration (17-26 mmol) of alkyl chain revealing that coating of cross -linked alkyl chitosan greatly enhanced the mechanical properties of higher tensile strength (upto 18.6 MPa) and tensile index (upto 30.2 N.m / g). Table 2 illustrates variation in the weight percentage of elements has and the effect for the combinations of chitosan, pentaerythritol triacrylate and ODA. Examples

[0093] The following examples are given by way of illustration of the working of the invention in actual practice and therefore should not be construed to limit the scope of the present invention in any way.

[0094] The provided examples are presented solely for the purpose of illustrating the functionality of the invention in practical applications. It is important to note that these examples are not intended to impose any limitations on the scope of the present invention.

[0095] Example 1: - Synthesis of Crosslinked Alkyl Chitosan

[0096] In a 1000 mL two-neck round bottom flask, the aqueous solution of chitosan (1.5 g) was prepared by using acetic acid (12 mL) and DI water (150 mL). Then, required amount of pentaerythritol triacrylate (PET) was added to the chitosan solution and the mixture was placed in a water bath pre-heated at 60 °C. The mixture was kept under stirring at 200 rpm for 2 hours. Meanwhile, an alcoholic solution of octadecyl amine (ODA) was prepared using required amount of ODA and 90 mL ethanol. The ethanolic solution of ODA was then dropwise added to the reaction mixture of chitosan and PET, and the reaction was continued for 2 more hours. Finally, a hazy dispersion was obtained which was cooled to room temperature and then transferred into air tight container. The molar ratio of PET and ODA was kept constant at 1:3 across all the batches. FIG. 1 shows the complete reaction pathway to crosslink chitosan by PET followed by functionalization with ODA.

[0097] Example 2:- Preparation of Coated Papers for Mulching

[0098] About 200 mL of the synthesized coating material was taken and diluted to 1000 mL with DI water (to adjust the solid content at 1.6-2.6 wt%) and applied as coatings on kraft papers (36 x 48 inches) by the dip-coating method as shown in the FIG. 3. The dip-coated kraft papers were air-dried at room temperature for 24-48 h before conducting the analysis of water repelling properties along with durability at outdoor environment. Coated kraft paper cannot be wetted by milk, juice and water while they can immediately wet the uncoated paper. These physically deposited beverages were easily wiped away and left behind a clean and dry surface whereas similar treatment cannot be done on the uncoated part.

[0099] The present study reveals the excellent water repelling property of coated kraft paper which is the most important property required for mulching application. We also examined the efficiency of coating in outdoor environment, where a piece of coated paper was kept outside. After 60 days, it was observed that the coated paper was still repelling the water. This study confirmed the suitability of our coated paper for mulching application where the mulch film should exhibit water repelling property during the crop season (usually 2-3 months).

[0100] Example 3:-Water Uptake analysis

[0101] The water uptake values of coated and uncoated paper were analysed by dipping the paper pieces (having dimension 4 cm x 4 cm) into 400 mL of water for 6 hours. The % of absorbed water was determined by weighing the wet paper in every one hour and the respective values are shown in FIG. 4. shows the trend of water uptake vs time for the uncoated and coated papers. The uncoated paper showed high water uptake value (118.2%) in 1 hour of dipping whereas the coated paper showed only 14.3% absorption. The maximum water absorption for uncoated paper reached to 127.3% in 4 hours, the same for coated paper was 42.8 %. As expected, the coated paper showed very less water uptake value compared to the uncoated paper.

[0102] Example 4:- Mechanical Property of Coated Kraft Papers

[0103] The mechanical behaviour of the coating is crucial for application appropriateness. The elongation and tensile strength of the coated and uncoated kraft papers (length = 15 cm, width = 1.5 cm) and were measured by a Universal Tensile Machine (UTM) of Dak System Inc. Series 7200 (Model T-72502) in line with ASTM standard D882. The uncoated kraft papers generally have poor mechanical properties as shown from the lower tensile strength (11.2 MPa). On the other hand, the kraft papers coated with different molar concentration (17-26 mmol) of alkyl chain (ODA) showed higher tensile strength (upto 18.6 MPa) and tensile index (upto 30.2 N.m / g) as shown in Table 1. It was evident from these results that the coating of crosslinked alkyl chitosan greatly enhanced the mechanical properties of kraft paper.

[0104] Table 1: shows the values of tensile strength and tensile index of the coated and uncoated Kraft Paper measured by UTM.

[0105]

[0106] Example 5:- Biodegradability of Coated Kraft Paper

[0107] The test for biodegradation was evaluated in terms of compostability which was conducted using a soil burial method. The samples measuring 5 x 4 cm was placed in vermi-compost at a depth of 10 cm surface. Sample compostability in soil or vermicompost is an energy saving and environmentally-friendly technique because it doesn't require a controlled environment or high temperatures. As a result, the kraft paper coated with crosslinked alkyl chitosan was buried for 45 days in horticultural vermicompost. Water was added at every 15 days for anaerobic decomposition, into the compost to maintain the moisture level. FIG. 5 shows the stages of degradation at every 15 days for 45 days. The noticeable change was observed like breakage and fragmentation of the coated Kraft paper. The respective FE-SEM images show the dramatic change in fiber morphology of the coated paper degraded at 30 days.

[0108] Example 6:-Biodegradable Coated Kraft Paper for Mulching

[0109] The coated kraft paper has been used for mulching application in melon cultivation for more than 64 days as shown in FIG. 6. The melon plants were found to come up at day 15 and continued to grow upto day 64 when it started producing melons and during this entire time, the paper mulch was found to be intact. Since the coated kraft paper can degrade naturally over time, there is no need of proper disposal. The developed paper-based mulch will be a perfect alternative to traditional plastic-based mulching materials, providing similar benefits while reducing waste and environmental impact.

[0110] Table 2 illustrates variation in the weight percentage of elements has and the effect for the combinations of chitosan, pentaerythritol triacrylate and ODA. However, the control experiments involving chitosan + ODA and chitosan + pentaerythritol triacrylate showed dramatic change in the mechanical property as measured by tensile strength and hydrophobicity as measured by water contact angle (WCA).

[0111] Table 2:- Variation in the weight percentage of elements

[0112] ADVANTAGES OF THE PRESENT INVENTION

[0113] The present disclosure described herein above has several technical advances including, but not limited to a biodegradable cross-linked alkyl polysaccharide coating dispersion material for lignocellulose sheets as an alternative to conventional plastic mulches. Specifically, the present invention relates to further alkylating cross-linked chitosan and coating it onto the surface of lignocellulose sheets for enhancing their tensile strength. More particularly the said coated lignocellulose sheets are applicable as mulch in farming to enhance the soil health by conserving the moisture, reducing soil erosion and suppressing weeds. The invention also relates to a method of coating and the process for the preparation of a biodegradable crosslinked alkyl polysaccharide dispersion material.

[0114] • To provide biodegradable crosslinked polysaccharide dispersion material with high tensile strength for lignocellulose sheets coating in high yield 93% to 95%.

[0115] • Higher mechanical strength (tensile index upto 30.2 N.m / g) compared to prior art.

[0116] • The coating material has high efficiency of in outdoor environment for 50-70 days.

[0117] • Enhanced hydrophobicity (WCA upto 125°) of the coated sheets makes it ideal alternative of plastic mulches. • Environmentally friendly, biodegradable Coating material for weed control, moisture retention, soil temperature regulation, erosion control, and enhances agricultural productivity, supports sustainable practices, and contributes to overall environmental health.

[0118] • Development of a cross-linked chitosan followed by further alkylation via Michael addition with improved mechanical strength and hydrophobicity simultaneously.

[0119] • The as developed chitosan-based coating material is bio-based, biodegradable and cost effective.

[0120] • The coated lignocellulose sheet / paper is characterized for hydrophobicity, mechanical property, water absorption, soil-compostability and mulching.

[0121] Finally, when used herein, the term “comprises” and its derivations (such as “comprising”, etc.) should not be understood in an excluding sense; that is, these terms should not be interpreted as excluding the possibility that what is described and defined may include further elements, steps, etc. Although the description herein contains many details, these should not be construed as limiting the scope of the disclosure but as merely providing illustrations of some of the presently preferred embodiments. Therefore, it will be appreciated that the scope of the disclosure fully encompasses other embodiments which may become obvious to those skilled in the art.

Claims

We claim:

1. A biodegradable cross-linked alkyl polysaccharide dispersion coating material coated on a lignocellulose sheet, comprises;(a) a polysaccharide;(b) an acrylic cross-linker; and(c) an alkyl amine R(CH2)nNH2; wherein n comprises an alkyl chain of 2-18 carbon atoms; wherein weight ratio of polysaccharide and acrylate cross-linker is 1:3 to 1:5; and wherein a molar ratio of the acrylic cross-linker and the alkyl amine is 1:3.

2. The biodegradable cross-linked alkyl polysaccharide dispersion coating material as claimed in claim 1, wherein the polysaccharide is chitosan and the acrylate crosslinker is selected from the group consisting of trimethylolpropane triacrylate, pentaerythritol triacrylate (PET) and a mixture thereof.

3. The biodegradable cross-linked alkyl polysaccharide dispersion coating material as claimed in claim 1, wherein the alkyl amine is selected from the group consisting of methyl amine, ethyl amine, 1 -propyl amine (n-propyl amine), 2-propyl amine, ethyl-propyl amine, methylhexyl amine, ethyl-methyl amine, cycloalkyl amine, octadecyl amine, alkenyl amine, alkynyl amine, aryl amine, arylalkyl amine, alkylaryl amine and a mixture thereof.

4. A process for preparation of biodegradable cross-linked alkyl polysaccharide dispersion material as claimed in claim 1, comprises:(a) preparing an aqueous solution of chitosan in acetic acid, and adding an acrylate crosslinker followed by heating the solution in a water bath at a temperature in the range of 50°C-70°C and stirring at 200-300 rpm for a time period in range of 1-3 hours;(b) adding ethanolic solution of alkyl amine drop-wise to the reaction mixture as obtained in step a) and keeping the reaction conditions constant for a time period in range of 1-3 hours to obtain a hazy dispersion;(c) cooling down the hazy dispersion as obtained in step b) to a temperature in the range of 20°C-30°C and storing in an air tight container to obtain a dispersion material;wherein the biodegradable cross-linked alkyl polysaccharide dispersion material is prepared by a Michael addition reaction of the polysaccharide chitosan, and the acrylic crosslinker followed by alkylation with the alkylamine; wherein the biodegradable cross-linked alkyl polysaccharide dispersion coating material is obtained in 93%-95% yield.

5. The biodegradable cross-linked alkyl polysaccharide dispersion coating material as claimed in claim 1, wherein the lignocellulose sheet / paper is selected from the group consisting of kraft paper, copy paper, card stock, news print, watercolour paper, Vellum, tracing paper, parchment paper and construction paper.

6. The biodegradable cross-linked alkyl polysaccharide coated sheet as claimed in claim 1, wherein the sheet is having a water absorption of 42.8 % when compare to uncoated sheets 127.3% in 4 hours.

7. The biodegradable cross-linked alkyl polysaccharide coated sheet as claimed in claim 1, wherein the sheet is having enhanced water repelling property for 2-3 months in outdoor environment and decompose naturally in the soil within 30-45 days.

8. The biodegradable cross-linked alkyl polysaccharide coated lignocellulose sheet as claimed in claim 1, wherein the sheet coated with different molar concentration (17-26 mmol) of alkyl chain is having tensile strength of 15-20 MPa (2450-2650 N / m), and tensile index of 25-30 N.m / g.

9. A process for preparation of biodegradable cross-linked alkyl polysaccharide dispersion material coated lignocellulose sheets as claimed in claim 1, comprising the steps of;(a) diluting the dispersion material of claim 1 with deionized water to five times followed by applying it for dip coating dispersion on the lignocellulose sheet;(b) air-drying lignocellulose sheets as obtained in step a) at a temperature in range of 20 °C- 30 °C for a time period in range of 24-48 hours.

10. The process as claimed in claim 9, wherein a molar ratio of the acrylate cross linker and the alkyl amine is 1:3.

11. The process as claimed in claim 9, wherein solid content in dispersion is 1.6-2.6 wt%.

12. The biodegradable cross-linked alkyl polysaccharide coated lignocellulose sheet as claimed in claim 1, wherein the dimension of the coated lignocellulose sheets are 36 x 48 inches.

13. The biodegradable cross-linked alkyl polysaccharide coated lignocellulose sheet as claimed in claim 1, wherein the coated lignocellulose sheets are for mulching of plants with crop duration of more than 50-70 days.

Images